Rotary expansible drilling apparatus with centrifugally operated latch



A R. o. PARK 3,351,144 ROTARY EXPANSIBLE DRILLING APPARATUS WITH CENTRIFUGALLY OPERATED LATCH 5 Sheets-Sheet 1 Lrahl.

Nov. 7, 1967 Filed April 5, 1965 R. O. PARK ROTARY EXPANSIBLE DRILLING APPARATUS WITH Nov. 7, 1967 CENTRIFUGALLY OPERATED LATCH 3 Sheets-Sheet 2 Filed April 5,. 1965 oEeT 0. pme/v l Veg y f/ y a m. a

Y Nov. 7, 1967 PARK 3,351,144

R. O. ROTARY EXPANSIBLE DRILLING APPARATUS WITH CENTRIFUGALLY OPERATED LATCH Filed April 5, 1965 5 Sheets-Sheet 3 IZ 3. lfra. l4.

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57g f? y ,0r faQ/vsn Patented Nov. 7, 1967 fornia Filed Apr. 5, 1965, Ser. No. 445,328 17 Claims. (Cl. 175-269) ABSTRACT F THE DISCLOSURE Rotary expansible drill bit apparatus for use in a well bore and having cutters expandable outwardly of the body of the -apparatus by hydraulic pressure, a centrifugally operated lock device preventing cutter expansion until released by centrifugal force incident to rotation of drill pipe to which the apparatus is secured, such centrifugal force being capable of releasing the lock device only if imposed prior to imposition of hydraulic pressure on the apparatus.

The present invention relates to subsurface well bore equipment, and more particularly to drilling apparatus having outwardly expandable cutters.

An object of the invention is to provide a control rnechanism for preventing the cutters of an expansible type of drill bit from being expanded outwardly from a retracted position, until desired.

Another object of the invention is to provide rotary drilling apparatus embodying a body and cutters mounted on the body which lare expandable outwardly as a result oi relative longitudinal movement of a mandrel or plunger along the body, in which such relative longitudinal movement of the mandrel or plunger can be prevented or permitted at the will of the operator.

A further object of the invention is to provide rotary drilling apparatus embodying a body and cutters mounted on the body which are expandable outwardly as a result of lluid pressure relatively shifting a mandrel or plunger along the body, in which such Huid pressure shifting of the Vmandrel 0r plunger can be selectively prevented or penrnitted.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and fonming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined .by the appended claims.

Referring to the drawings:

FIGURES la and lb together constitute a longitudinal section through an apparatus disposed in a well bore with expandable cutters disposed in a retracted position and with the control portion of the apparatus located in its latching position, FIG. lbbeing a lower continuation of FIG. la;

FIGS. 2a and 2b are views corresponding to FIGS. la and 1b, respectively, illustrating the apparatus with its cutters in their fully expanded position, FIG. 2b being a lower continuation of FIG. 2a;

FIG. 3 is an enlarged fragmentary longitudinal section through the lock portion of the apparatus, illustrated in its locking position;

FIG. 4 is a View similar to FIG. 3 illustrating the lock portion of the apparatus in unlatched or unlocked position;

FIG. 5 is a cross-section taken along the lines 5-5 on FIG. 3.

A rotary expansible drill bit A, of a known type, s disclosed in the drawings, that has initially retracted cutter members 10 that are adapted to be expanded outwardly for the purpose of enlarging the diameter of a well bore B in which the apparatus is lowered. A control mechanism or unit C is operatively attached to the expansible rotary drill bit for the purpose of selectively determining the ability of the cutters 10 to be expanded outwardly. Such control unit can prevent or permit expansion of the cutter members.

In the specic expansi-ble rotary drill bit disclosed, an elongate tubular body 11 is provided having a plurality of longitudinal slots 12 therein, each of which receives a cutter member .10 pivotally mounted on a hinge pin 13 extending across the slot and suitably secured to the body. The cutters are normaly in a pendant position within the body 11, the outer surfaces 14 of the cutters preferably lying within the contines of the body periphery. They are expandable outwardly of the body as a result of downward movement of a tubular piston plunger device 15 slidable within the bore 16 of the body. As shown, the

1ncludes a lower section 17 slidable in the bore of the body below the slots 12 and having 18 engaging gear teeth 19 on the cutter members. The upper end of the lower section 17 is threadedly secured to the lower end of an upper plunger section 20 that extends within the central body passage above the slots 12, this upper section having a piston head 21 slidable along the inner wall 22 of the upper cylinder portion 23 of the tubular body. A helical cornpression re'tracting spring 24 encompasses the upper secf tion of the tubular piston plunger device, its lower end bearing against an upwardly facing body shoulder 25 and its upper end engaging the piston head 21, urging the entire plunger device 15 in an upward direction within the body, and tending to hold it in an upward position in which the cutter members 10 are retracted.

`When iluid is pumped downwardly through the apparatus a pressure differential developed above the piston gear teeth 19 and swing the cutter members outwardly and upwardly to their fully expanded position, such as disclosed in FIG. 2b. Leakage of iluid around the piston head is prevented by suitable side seal rings 26 thereon slidably and sealingly engaging the cylinder wal-l 22; whereas leakage of fluid around the lower portion of the plunger device is prevented `by one or more suitable side seal rings 27 thereon engaging the cylindrical wall 28 of the body below the slots 12. A suitable back pressure can 'be built up for action ron` a downward direction on the piston head 21 by securing a suitable oriiice or bean 29 in the lower end of the tubular plunger device 15. As uid is pumped downwardly through the tubular plunger device ia certain portion thereof in its passage 30 can discharge through nozzles 31 and through the body slots 12 into the well bore B for the purpose of removing the cuttings and ilushing them around the exterior of the apparatus to the top of the Well bore.

The control unit C is secured to the expansible drill bit A so as to ascertain the ability of the fluid pressure pumped down through the apparatus to shift the plunger device 15 downwardly in the body and effect outward expansion of the cutters, or to prevent the fluid pressure from moving the plunger 15 downwardly. As shown, the control unit includes a body or housing 35 having a lower threaded pin 36 Ithreadedly secured within the upper threaded box 37 of the expansible bit body 11. The upper end of the body or housing may be constituted as a threaded box 38 receiving the lower pin end 39 of the drill pipe D that will extend upwardly in the well 'bore to the top thereof. A tubular piston rod or extension 40 is threadedly secured to the upper end of the plunger device 15 and extends upwardly within the control unit body or housing 35. An adjustment sleeve 41 of the piston rod extension 40 is disposed around the main portion 42 of the piston rod extension and is adjustably connected thereto by threads 43 so that the longitudinal position of the sleeve with respect to the remainder of the extension rod can be determined. This sleeve has opposed lugs or ears 44 integral therewith and extending into slots or grooves 45 in lock members 46 which are pivotally mounted on the lugs by pivot pins 47. Each lock member has a lower lock portion or arm 48 depending from the pin and adapted to engage an upwardly facing latch or lock shoulder 49 formed in the housing 35. Each lock lmember also includes an upper weight portion or arm 50, arcuate in shape, which tends to move outwardly under the action of centrifugal force incident to rotation of the apparatus, and which is normally yieldably urged in a lateral inward direction by leaf springs 51 interconnecting opposed ends of the weighted arm portions 50. As shown two pairs of leaf springs 51 are disposed diagrammatioally opposite each other externally of the adjustment sleeve 41, the lower ends of the leaf springs being suitably secured, as by means of screws 52, to the opposed weighted arm members, and their upper ends being -secured to one another in any suitable manner, as by means of a bolt 53. The leaf springs 51 tend to move toward each other to retain the weight arms 50 in their inward position, which, because of the fact that the lower lock portions of ar-ms 48 are disposed on the opposite side of the fulcrums or hinge pins 47, will urge such arms in an outward direction and in a -position in which the lower ends 55 of the lock arms can engage the upwardly facing shoulder 49.

As shown, the lower ends 55 of the lock arms are inclined in an outward and downward direction in order to engage a companion inclined lock shoulder 49. As a result, with the lock arms 48 engaging the shoulder 49, any tendency for the weighted portions 50 of the levers 46 to 'swing outwardly cannot shift the lower arm .portions inwardly to a position released from the lock shoulder 49. The weighted arm portions 50 can only swing outwardly under the action of centrifugal force when the lower arms 48 are elevated from the upwardly facing latch shoulder 49. The appropriate position of t-he lower ends 55 of the lower lock arms with respect to the .shoulder 49, when the expandable cutters are in their retracted position and the apparatus is stationary, with no fluid pressure being pumped therethrough, can be determined by suitably threading the adjustment sleeve 41 .along the main portion 42 of t-he piston rod or extension 40. When the proper adjustment has been made, the sleeve can be retained in such position by means of a set screw 58 bearing against the main portion of the piston rod.

When the the arms 48 engaging the body shoulder 49, the downward thrust of the piston trod extension 40 on the lock members 46 is prevented from passing through the hinge pins 47 by causing the hinge pins to have a loose fit in the bores 60 in the lugs 44 through which they pass, so that the lower end l61 of the adjusting sleeve 41 will engage a thrust shoulder 62 on each lock member 46 land transmit the downward force directly to the lower arm portion 48 and to the upwardly facing latch shoulder 49 of the control unit body 35.

As shown in the drawings, the piston rod extension 40 is tubular and has a central passage 65 therethrough cornmunicating with the passage 30 in the tubular piston plunger device 15. The piston rod extension has a plurality of side ports 66 below the control unit body communicating with the central passage 65 through the piston rod extension and opening into the cylinder 23 above the piston head. Leakage of iluid between a lower head portion 68 of the piston rod extension and the control unit -control unit is in its locked position, with body 35 is prevented by a suitable side seal ring 69 mounted on the body and slidably and sealingly engaging the periphery of the head. The adjustment sleeve 41 eX- tends through a ring 70 bearing against an upwardly facing body shoulder 71, this ring having `an inner side sealing ring 72 slidably and sealingly engaging the periphery of the adjustment sleeve and an outer side seal ring 73 sealingly engaging the wall of the housing 35. Leakage of fluid between the main portion 42 `of the piston rod extension and the adjustment sleeve 41 is prevented by a suitable side `seal ring 74 on the` rod engaging the adjustment sleeve.

The sealing of the periphery of the head 68 against the wall of the housing 35 and of the adjustment sleeve 41 against the balance ring 70 will prevent drilling mud and undesired substances from entering an annular chamber 75 formed between the piston trod extension 40 and the body or housing 35, and in which the lock members 46 are mounted. Accordingly, there will be no interference with the movement of the lock members between their locked and unlocked positions. If desired, to facilitate freedom of movement of these parts, a body of oil 76 can be inserted through an opening 77 in the wall of the housing int-o the chamber, the opening being closed by :a suitable plug 78.

The lower end of the drill bit body 11 may be constituted at a lower threaded box 79 which can be threadedly connected to the upper pin end 80 of a lower tool E, which, for example, may be an expansible drill bit that can be the same as the expansble drill bit A illustrated in the drawings, or which may be an ordinary drilling bit. For that matter, it may be constituted as a casing milling device. Such lower tool E can be operated to accomplish its drilling function while retaining the cutter members 10 of the expansible rotary drill bit A, `to which the control unit is attached, in their retracted position during the pumping of the drilling fluid through the drill pipe D and the apparatus. The control unit C can be manipulated at any time to permit the uid under pressure being pumped through the apparatus to expand the cutter members 10 outwardly.

In a typical use ofthe is secured to the lower end of the expansible drill bit A, and the drill pipe D is attached to the body or housing 35 of the control unit. The springs 51 urge the weight members 50 inwardly and the lower lock arms 48 outwardly, as disclosed in FIG. la, with the lower ends 55 of the lock arms being disposed above the latch shoulder 49. The apparatus is lowered in the well bore to the desired operating point therewithin by means of the drill pipe D. Assuming it is desired to retain the cutter members 10 in their retracted position, fluid under pressure is pumped down through -the drill pipe D and through the apparatus C, A, E without rotating the apparatus. Such fluid pressure will pass through the extension passage 65 and the ports 66 into the cylinder 23, and will act in a downward direction on the piston head 21 tending to shift the piston head downwardly. However, the piston head can `only move downwardly to the slight extent at which the latch arms 48 are moved downwardly into engagement with the body shoulder 49 therebelow, as disclosed in FIG. 3, the cutter members 10 remaining in their retracted position since the tubular pis-` ton plunger device is prevented from having any significant downward movement withinthe body 11 to swing the cutter members Iy10 outwardly. The fluid under pressure can pass down through the central passage 30 through the tubular piston plunger device and through the bean 29 into the lower tool E for discharge therefrom.

The drill pipe D and apparatus connected thereto can then be rotated, the lower tool E being rotated to perform its required function. If such lower tool is a bottom hole drilling bit it will act upon the bottom of the hole anddrill away the formation, drilling fluid being pumped through the apparatus in order to carry the cuttings away from the drilling region and upwardly around the apparatus and the drill pipe to the top of the well bore. Such rotary action apparatus disclosed, a drill bit l5.A

tends to cause the weight portions 50 of the locks 46 to swing outwardly under the action of centrifugal force, and against the force of their Iretracting springs 51, but they cannot do so since the fluid pressure is holding the lock arms 48 downwardly against the shoulder 49, the arms 48 and shoulder 49 having a negative angle of engagement to retain the lock arms 48 in their outward position.

If the lower tool E is an expandable type of drill bit, Without a control unit C connected thereto, then the pumping of iluid downwardly through the apparatus will cause the piston plunger device 15 of such lower tool to move downwardly and expand its cutters outwardly. However, the cutter members 10 of the apparatus illustrated, t0 which the control unit C is secured, cannot 'be expanded outwardly since piston plunger device 15 is prevented from moving downwardly to any significant extent.

When it is desired to expand the cutter members 19 outwardly, the pumping of fluid through the drill pipe D and the apparatus C, A is stopped, which will relieve the pressure acting downwardly on the piston head 2l and allow the retracting spring 2,4 to shift the piston plunger device 15 upwardly, as well as the piston rod extension 40 attached thereto, for the purpose of elevating the lower latch arms 48 above the lock shoulder 49, the parts then being in the position illustrated in FIGS. la and 1b. Prior to repumping fluid through the drill pipe and the apparatus, the drill string and the apparatus are rotated, which will cause centrifugal force to shift the weighted arms 5i) outwardly and the lower lock arms 48 inwardly against the periphery of the piston rod extension 40, the lock arms 48 then being disposed out of alignment with the housing lock shoulder 49. Fluid under pressure can then be pumped downwardly through the drill pipe and the apparatus, passing outwardly through the ports 66 into the cylinder 23 for downward action on the piston head 21, shifting the piston plunger device 15 downwardly and causing the circular rack teeth 18 to engage the gear teeth 19 on the cutter members and expand the latter outwardly to the position disclosed in FIG. 2b. At that time, the lower lock arms 48 will be moved downwardly within a smaller diameter portion 95 of the housing below the shoulder 49, as disclosed in FIGS. 2a -and 4. Rotation of the apparatus C, A while drilling lluid is pumped downwardly therethrough can continue, the cutter member operating upon a formation shoulder F for the purpose of enlarging the diameter of the well bore B, as disclosed in FIG. 2b.

At any time, the control unit C can be reactivated. All that need be done is to stop its rotation and the pumping of fluid therethrough, which will allow the retracting spring-24 to re-elevate the plunger device 15 and rod extension 40, as well as the lock members 46, within the tubular body 11 and the housing 35, the lower lock arms 48 being again disposed out of the restricted downward portion 95 of the housing, allowing the springs 51 to retract the weight portions 50 of the arms inwardly and swing the lower lock arms 48 outwardly to a position above the lock shoulder 49. The upward shifting of the piston plunger device 15 will effect retraction of the cutter members 10. If it is desired to retain the cutter members in a retracted position, it is only necessary to pump fluid downwardly through the drill pipe D and the apparatus C, A prior to their rotation, so that the lower arms 48 will again be moved downwardly against the lock shoulder 49. As was pointed out above, the downward thrust between the piston rod extension 40 and the housing 35 is transmitted directly from the lower end 61 of the adjustment sleeve to the lower lock arms 48 to the lock shoulder 49, without being required to pass through the hinge pins 47, which fit loosely in the holes 60 in the lugs 44.

For the purpose of preventing fluid pressure being pumped through the apparatus from acting on the piston rod extension 40 itself and tending to shift it downwardly in the housing, the cross-sectional area S between the inner wall of the piston rod extension and the exterior of the adjustment sleeve 41 can be made substantially equal to lthe cross-sectional area R between the inner wall of the head 68 of the piston rod extension and its periphery. The fluid pressure passing through the piston rod extension will be acting over equal and opposite areas R and S in an upward and downward direction and will not tend to shift the piston rod extension longitudinally in the body or housing 35. Preferably, the area R may be made slightly greater than the area S so that there is a resultant area over which iiuid pressure acts tending to shift the piston rod extension in an upward direction. However, in View of the much greater cross-sectional area of the piston head 21, there is very little resistance to downward movement of the piston plunger device 15 when fluid pressure is pumped downwardly through the apparatus for the purpose of expanding the cutter members =10 outwardly.

Although disclosed as an apparatus for enlarging the diameter of the well bore B, the cutter members 10 could be constituted as milling cutters for milling away a section of well casing, or the like. Similarly, the lower tool E could be a casing milling tool of any suitable specific type, as, for example, the specific type of expandable bit A illustrated, and its cutters 10 would first be expanded outwardly to mill away a portion of the casing, the control unit C preventing the cutters of the upper tool from being expanded outwardly until the lower set of cutters have been expanded. Thereafter, the control unit C -can be released from its locked position and placed in a condition in which the weighted arm members 50 can swing outwardly and shift the lower lock arms 48 inwardly to a position released from the shoulder 49, allowing the upper set of cutter members 10 to be expanded outwardly.

I claim:

1. In rotary expansible drill bit apparatus adapted to be lowered in a well bore: a rotary drill bit having noramally retracted cutter means shiftable laterally outwardly; actuating means movable in one direction for shifting said cutter means laterally outwardly; means connected to said actuating means to prevent said actuating means from shifting said cutter means laterally outwardly; means for releasing said preventing means independently of actuation of said actuating means` in shifting said cutter means laterally outwardly; means engaging said actuating means for moving said actuating means inthe opposite direction to shift said cutter means from its later-` ally outward position to retracted position while said apparatus is in the well bore; and means for replacing said preventing means in its position preventing actuation of said actuating means while said apparatus is in the well bore and after shifting of said cutter means to retracted position.

2. In rotary expansible drill bit apparatus: drill bit lhaving normally retracted cutter means laterally outwardly; actuating means for shifting said cutter means laterally outwardly; actuating means for shifting said cutter means laterally outwardly; means connected to said actuating means to preventsaid actuating means from shifting said cutter means lateraly outwardly; means movable in a laterally outward direction in response to rotation of said apparatus; and means connecting said laterally movable means to said preventing means whereby said lateral outward movement of said laterally movable means shifts said preventing means to a released position.

3. In rotary expansible drill bit apparatus adapted to be Vlowered in a well bore: body means; cutter means mounted on said body means and shiftable laterally outwardly thereof; actuating means connected to said cutter means and movable longitudinally of said body means in one direction for shifting said cutter means laterally outwardly; lock means connected to said actuating means to prevent said actuating means from shifting said cutter means laterally outwardly; means for releasing said lock means independently of movement of said actuating a rotary shiftable means longitudinally of said body means; means engaging said actuating means for moving said actuating means in the-opposite direction to shift said cutter means from its laterally outward position to retracted position while said apparatus is in the well bore; and means for relooking said lock means While said apparatus is in the well bore and after shifting of said cutter means to retracted position.

4. In rotary eX-pansible drill bit apparatus: body means; cutter means mounted on said body means and shiftable laterally outwardly thereof; actuating means connected to said cutter means and movable longitudinally of said body means for shifting said cutter means laterally outwardly; lock means connected to said actuating means to prevent said actuating means from shifting said cutter means laterally outwardly; centrifugally operated means responsive to rotation of said body means; and means connecting said centrifugally operated means to said lock means whereby lateral outward movement of said centrifugally operated means shifts said lock means to a released position permitting said actuating means to shift said cutter means laterally outwardly.

5. In rotary expansible drill bit apparatus: body means having a uid passage therethrough; cutter means mounted on said body means and shiftable laterally outwardly thereof; liuid pressure responsive actuating means connected to said cutter means and movable longitudinally of said body means by uid pressure in said passage to shift said cutter means laterally outwardly; lock means connected to said actuating means to prevent fluid pressure in said passage from shifting said actuating means longitudinally of said body means; centrifugally operated means responsive to rotation of said body means; and means connecting said centrifugally operated means to said lock means whereby lateral outward movement of said centrifugally operated means shifts said lock means to a released position permitting said actuating means to shift said cutter means laterally outwardly.

6. In rotary expansible drill bit apparatus: body means; a cutter mounted on `said body means and shiftable laterally outwardly thereof; actuating means connected to said cutter and movable longitudinally of said body means for shifting said cutter laterally outwardly; a lock member carried by one of said means and engageable with the other of said means to prevent said actuating means from shifting said cutter laterally outwardly; centrifugally operated means responsive to rotation of said one of said means; and means connecting said centrifugally operated means to said lock member whereby lateral outward movement of said centrifugally operated means 'shifts said lock member to a released position permitting said actuating means to shift said cutter means laterally outwardly.

7. In rotary expansible drill bit apparatus: body means having a fluid passage therethrough; a cutter mounted on said body means and shiftable laterally outwardly thereof; fluid pressure responsive actuating means connected to said cutter and movable longitudinally of said body means by uid pressure in said passage to shift said cutter laterally outwardly; a lock member carried by one of said means and engageable with the other of said means to prevent fluid pressure in said passage from shifting said actuating means longitudinally of said body means; centrifugally operated means responsive to rotation of said one of said means; and means connecting said centrifugally operated means to said lock member whereby lateral outward movement of said centrifugally operated means shifts said lock member to a released position permitting said actuating means to shift said cutter means laterally outwardly. n

8. In rotary eXpansible drill bit apparatus: body means having a uid passage therethrough; cutter means mounted on said body means and shiftable laterally outwardly thereof; actuating means connected to said cutter means and movable downwardly in said body means by uid 81 pressure in said passage to shift said cutter means laterally outwardly; a lock member carriedby said actuating means and engageable with said body means to prevent duid pressure in said passage from shifting said actuating means downwardly in said body means; and centrifugally operated means responsive to rotation of said body means and actuating means for releasing said lock member from said body means.

9. -In rotary expansible drill bit apparatus: body means having a fluid passage therethrough; cutter means mounted on said body means and shiftable laterally outwardly thereof; actuating means connected `to said cutter means and movable downwardly in said body means by fluid pressure in said passage to shift said cutter means lateral-` ly outwardly; lock means pivotally carried by-said actuating means and comprising a lower arm portion engageable with said body means to prevent uid pressure in said passage from shifting said `actuating means down- Wardly in said body means, said locking means also including a centrifugally actuated upper arm portion rcsponsive to rotation of said body means and actuating means to release said lower arm portion from said body means.

10. In rotary expansible drill bit apparatus: a lower body having a fluid passage therethrough; cutter means mounted on said body and shiftable laterally outwardly thereof; a fluid pressure responsive plunger device c0nnected to `said cutter means and movable downwardly in said body by duid pressure in said passage to shift said cutter means laterally outwardly; an upper body secured to said lower body; an extension member secured to said plunger device and extending upwardly therefrom into said upper body; a lock member carried by said extension member and engageable with said upper body to prevent uid pressure in said passage of a value suicient to shift said cutter means laterally outwardly from shifting said extension member and plunger device downwardly in said bodies; and means for disengaging said lock member from said upper body to permit downward movement of said extension member and plunger device.

11. In rotary expansible drill bit apparatus: a lower body having a duid passage therethrough; cutter means mounted on said body and shiftable laterally outwardly thereof; a plunger device connected to said cutter means and movable downwardly in said body `by uid pressure in said passage to shift said cutter means laterally outwardly; an upper body secured to said lower body; an extension member secured to said plunger device and extending upwardly therefrom upper body having an upwardly facing shoulder; a lock member pivotally carried by said extension member and having a lower arm portion engageable with said shoulder to prevent fluid pressure in said passage from shifting said extension member and plunger device downwardly in said bodies; said lock member having an upper weight portion shiftable laterally outwardly by centrifugal force upon rotationof said bodies to shift said lower arm portion inwardly from said shoulder.

12. In rotary expansible drill bit apparatus as defined in claim 11; wherein said extension member comprises a main portion and a sleeve portion adjustably threaded on said main portion, and wherein said lock member is pivotally mounted on said sleeve portion.

13. In rotary expansible drill bit apparatus: a lower body having a fluid passage therethrough; cutter means mounted on said body and shiftable laterally outwardly thereof; a plunger device connected to said cutter means and movable downwardly in said body by uid pressure in said passage to shift said cutter means laterally outwardly; an upper body secured to said lower body; a tubular extension member secured to said plunger device and longitudinally `slidable in said upper body; a lock member carried by said tubular extension member and engageable with said upper `body to prevent fluid presinto said upper body; said 1 sure in said passage from shifting said extension member and plunger device downwardly in said bodies; means for disengaging said lock member from said upper body to permit downward movement of said tubular extension member and plunger device; means providing a slidable seal between said extension member and body above said lock member; means providing a slidable seal between said tubular extension member and body below said lock member; said tubular extension member having an upwardly facing area above said upper seal `and subject l to iluid pressure in said bodies which is substantially equal to a downwardly facing area of said tubular extension member below said lower seal and subject to fluid pressure in said bodies.

14. In a control unit for an expansible rotary drill bit having cutter means and shiftable means for expanding the cutter means: a body having a connection for securing said body to the drill bit; an extension member slidable longitudinally in said body and having means for connecting said extension member to the expanding means; a lock member carried by said extension member and engageable with said body to prevent said extension member from shifting longitudinally in said body; and centrifugally operated means responsive to rotation of said body for shifting said lock member from said body to a released position.

15. In a control unit for an expansible rotary drill bit having cutter means and shiftable means for expanding the cutter means: a body having a connection for securing said body to the drill bit, said body having an upwardly facing shoulder; an extension member slidable longitudinally in said body and having means for connecting said extension member to the expanding means; a lock member pivotally carried by said extension member and having a lower arm portion engageable with said shoulder to prevent fluid pressure in said body from shifting said extension member downwardly in said body; said lock member having an upper weight portion shiftable laterally outwardly by centrifugal force upon rotation of said body to shift said lower arm portion inwardly from said shoulder.

16. In a control unit for an expansible rotary drill bit as defined in claim wherein said extension member comprises a main portion and a sleeve portion adjustably threaded on said main portion, and wherein said lock member is pivotally mounted on said sleeve 5 portion.

17. In a control unit for an expansible rotary drill bit having cutter means and shiftable means for expanding the cutter means: a tubular body having a connection for securing said body to the drill bit, said body having an upwardly facing shoulder; a tubular extension member slidable longitudinally in said body and having means for connecting said extension member to the expanding means; a lock member pivotally carried by said extension member and having a lower arm portion engage- 15 able with said shoulder to prevent uid pressure in said body from shifting said extension member downwardly in said body; said lock member having an upper weight portion shiftable laterally outwardly by centrifugal forces upon rotation of said body to shift said lower arm portion inwardly from said shoulder; means providing an upper slidable seal between said extension member and body above said lock member; means providing a lower slidable seal between said extension member and body below said lock member; said tubular extension member having an upwardly facing area above said upper seal and subject to fluid pressure in said body which is substantially equal to a downwardly facing area of said tubular extension member below said lower seal.

References Cited UNITED STATES PATENTS 735,930 8/1903 Worth 73-546` X 1,675,325 7/1928 Blanchard 175-267 1,801,552 4/1931 Grant 175-277 1,804,850 5/1931 Triplett 175-277 X 2,049,450 8/1936 Johnson 175-267 X 2,754,089 7/1956 Kammerer 175-277 X 2,809,016 10/ 1957 Kammerer 175-267 CHARLES E. oCoNNELL, Primary Examiner.

IAN A. CALVERT, Assistant Examiner. 

1. IN ROTARY EXPANSIBLE DRILL BIT APPARATUS ADAPTED TO BE LOWERED IN A WELL BORE; A ROTARY DRILL BIT HAVING NORMALLY RETRACTED MEANS SHIFTABLE LATERALLY OUTWARDLY; ACTUATING MEANS MOVABLE IN ONE DIRECTION FOR SHIFTING SAID CUTTER MEANS LATERALLY OUTWARDLY; MEANS CONNECTED TO SAID ACTUATING MEANS TO PREVENT SAID ACTUATING MEANS FROM SHIFTING SAID CUTTER MEANS LATERALLY OUTWARDLY; MEANS FOR RELEASING SAID PREVENTING MEANS INDEPENDENTLY OF ACTUATION OF SAID ACTUATING MEANS IN SHIFTING SAID CUTTER MEANS LATERALLY OUTWARDLY; MEANS ENGAGING SAID ACTUATING MEANS FOR MOVING SAID ACTUATING MEANS IN THE OPPOSITE DIRECTION TO SHIFT SAID CUTTER MEANS FROM ITS LATERALLY OUTWARD POSITION TO RETRACTED POSITION WHILE SAID APPARATUS IS IN THE WELL BORE; AND MEANS FOR REPLACING SAID PREVENTING MEANS IN ITS POSITION PREVENTING ACTUATION OF SAID ACTUATING MEANS WHILE SAID APPARATUS IS IN THE WELL BORE AND AFTER SHIFTING OF SAID CUTTER MEANS TO RETRACTED POSITION.
 14. IN A CONTROL UNIT FOR AN EXPANSIBLE ROTARY DRILL BIT HAVING CUTTER MEANS AND SHIFTABLE MEANS FOR EXPANDING THE CUTTER MEANS: A BODY HAVING A CONNECTION FOR SECURING SAID BODY TO THE DRILL BIT; AN EXTENSION MEMBER SLIDABLE LONGITUDINALLY IN SAID BODY AND HAVING MEANS FOR CONNECTING SAID EXTENSION MEMBER TO THE EXPANDING MEANS; A LOCK MEMBER CARRIED BY SAID EXTENSION MEMBER AND ENGAGEABLE WITH SAID BODY TO PREVENT SAID EXTENSION MEMBER FROM SHIFTING LONGITUDINALLY IN SAID BODY; AND CENTRIFUGALLY OPERATED MEANS RESPONSIVE TO ROTATION OF SAID BODY FOR SHIFTING SAID LOCK MEMBER FROM SAID BODY TO A RELEASED POSITION. 